Mattress



FIG. 1 is an isometric view of a top, front, and right side of an ornamental design for a mattress;

FIG. 2 is a front elevational view of the mattress of FIG. 1;

FIG. 3 is a rear elevational view of the mattress of FIG. 1;

FIG. 4 is a right side elevational view of the mattress of FIG. 1;

FIG. 5 is a left side elevational view of the mattress of FIG. 1;

FIG. 6 is top plan view of the mattress of FIG. 1; and,

FIG. 7 is a bottom plan view of the mattress of FIG. 1.

The dashed surface pattern and the dash-dash-dash-dash broken lines represent environmental structures that form no part of the claimed design. The dash-dot-dash-dot broken lines depict a symbolic break in the length and width of the mattress. The appearance of any portion of the article between the unclaimed dash-dot-dash-dot break lines forms no part of the claimed design. Further, the broken line cross-hatching is a portion that forms no part of the claimed design. 

CLAIM The ornamental design for a mattress, as shown and described. 